An ambiguity in the claims may lead to an insufficiency objection. However, ambiguity also relates to the scope of the claims, i.e. Art. 84 (see F‑IV, 4). Normally, therefore, an ambiguity in a claim will lead to an objection under Art. 83 only if the whole scope of the claim is affected, in the sense that it is impossible to carry out at all the invention defined therein. Otherwise an objection under Art. 84 is appropriate (see T 608/07).
In particular, where a claim contains an ill-defined ("unclear", "ambiguous") parameter (see also F‑IV, 4.11), and the skilled person is not able, on the basis of the disclosure as a whole and using his common general knowledge, to identify (without undue burden) the technical measures necessary to solve the problem underlying the application at issue, an objection under Art. 83 should be raised. The issue in case of an ill-defined parameter, that the skilled person would not know whether he was working within or outside of the scope of the claim, relates to a lack of clear definition and is independently a matter for objection under Art. 84. See T 593/09.
There is a delicate balance between Art. 83 and Art. 84, which has to be assessed on the merits of each individual case. Care has therefore to be taken in opposition that an insufficiency objection is not merely a hidden objection under Art. 84, especially in the case of ambiguities in the claims (T 608/07). On the other hand, even though lack of support/clarity is not a ground for opposition (see also F‑IV, 6.4), a problem related to it may in fact be of concern under Art. 83.